Frusto conical combustion chamber and method of making same



March 24, 1959 G. BURRELL 2,878,800

FRUSTO CONICAL COMBUSTION CHAMBER AND METHOD OF MAKING SAME Filed Dec. 31. 1954 2 Sheets-Sheet 1 INVENTOR ATTORN E Y March 24, 1959 G. BURRE-LL'. 2,878,800

FRUSTO CONICAL COMBUSTION CHAMBER AND METHOD OF MAKING SAME Filed Dec. 31. 1954 2 Sheets-Sheet 2 INVENTOR v '5 625m flawef! ATTORNEY United FRUSTO 'CONICAL COMBUSTION CHAMBER AND METHOD OF MAKING SAME Gilbert Burrell, Lansing, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 31, 1954, Serial No. 479,142

4 Claims. (Cl. 123-191) tes Patent Patented Mar. 24, 1959 ders 12 and to which finished plane surfaces on the inner walls 14 of the heads 13 are secured by bolts 16 projecting through the heads. Pistons 17 are reciprocably mounted in the cylinders 12 in such a way that at the outer dead center positions of the pistons the outer end surfaces of this pistons are substantially flush with the I plane end surfaces of the block 11 to which the heads erations on the surfaces forming the cavities. In high speed, high compression ratio engines for automotive and other uses it has been found that cavities formed by casting and without finishing the surfaces of the cavities are likely to vary in size, thereby making the operation of the engines unsatisfactory. When these wedge-shaped chambers are made so that it is possible to position the spark plugs near the volumetric center of the chambers, it is ditficult not only to cast but to finish the chambers, unless the chambers are made in a shape that does not quite fit the ends of the cylinders with which the cavities must cooperate in forming the combustion chambers for an engine. It has been the practice heretofore to make these cavities somewhat wider than the cylinders at the thin edges of the cavities, thereby providing relatively deep pockets projecting radially beyond the cylinders. These pockets tend to cause preignition and to result in unsatisfactory operation of the engine.

It is now proposed to form wedge shape cavities that are frusto conical in formation and that substantially fit the ends of the cylinders of the engine, particularly at the thin edges of the cavities where the preignition pockets have been previously formed. It is also proposed to provide a method of finishing that does not form excessive pockets at the thin edges of the cavities.

In the drawings:

Figure 1 is an end elevational view of an engine with parts thereof broken away to illustrate frusto conical cavities formed in the heads of the engine and which cooperate with the pistons and cylinders to provide the combustion chambers for the engine.

Figure 2 is a fragmentary plan view of one of the engine heads and illustrating one of the frusto conical cavities formed in the head and the relation of this cavity to a cylinder of the engine indicated by the broken circular line thereon.

Figure 3 is a fragmentary cross-sectional view of one of the engine heads and illustrating the operation of a tool employed in finishing one of the combustion chamber cavities in the head.

Figure 4 is a fragmentary plan view of the head illustrated by Figure 3 and showing the progress of the tool in its movement throughout the series of steps involved in the finishing of one of the combustion chamber cavities therein.

The engine 10 embracing the invention comprises an engine block 11 in which rows of cylinders 12 are formed and to which heads 13 are secured over the ends of the cylinders 12. The block 11 has normally disposed and finished plane surfaces thereon at the ends of the cylin- 13 are secured. Combustion chambers 18 are formed by the cavities 19, the cylinders 12 and the pistons 17. Inlet valves 21 and exhaust valves 22 for each cylinder of the engine open into the combustion chambers 18 by operation of the valve actuating mechanism of the engine and for controlling inlet passages 23 and exhaust passages 24 respectively. The passages 23 and 24 terminate in aligned ports opening into the cavities 19.

The cavities 19 may be cast or otherwise formed in the inner walls 14 of the heads 13. If the heads are made by casting, it is considered desirable to finish the outer surfaces of the inner walls 14 by removing the metal between the dot and dash line 26 and the finish line 27 to provide the plane'surfaces to be secured to the plane surfaces on the block 11 surrounding the cylinders 12. The cavities 19 are preferably cast in the inner walls 14 by employing cores or molds of frusto conical formation and which project into the heads in oblique relation to the finished surface 27 and the axes of the cylinders 12. The dot and dash line 28 indicates the unfinished configuration of one of the cavities 19 as formed by the cores or molds employed in the casting process.

In order to provide combustion chambers for the engine that do not vary materially in size, it is considered desirable to finish the cavities 19 by removing the metal between the dot and dash line 28 and the line 29. It is proposed to do this by employing a frusto conical metal cutting and finishing tool such as that indicated at 31 and with the larger end of the tool forming the inner part of the cavity. The tool 31 may be rotated upon the axis of the shaft 32 and may be rotated about an axis of rotation 33 at the center of the frusto conical surface represented by the line 29 and illustrating the finished surface of the cavity 19. When so rotated the axis of rotation of the shaft 32 will follow the dot and dash line indicated at 34. Figure 4 illustrates the line of the tool 31 at positions 36, 37, 38 and 39, which the tool may occupy during the finishing of the cavities 19. It will be noted that in position 36 the tool may be rotated upon the axis of the shaft 32 without engaging any part of the side wall 41 of the cavity 19. However, the large end of the tool 31 will be in a position to remove metal from the inner end surface of the cavity between the lines 28 and 29. As the tool 31 is rotated upon the axis of the shaft 32 and about the point 33 the tool will move from position 36 to positions 37, 38 and 39 and will return to position 36 at the end of one revolution about the axis through the point 33. As the tool moves from position 36 to position 37 it will be apparent that the side of the tool will commence to cut the side wall 41 of the cavity and will continue to cut the side wall of the cavity until the tool again approaches position 36. At position 36 it will be apparent that the tool 32 can be moved axially inwardly and outwardly of the head 13 without destroying the overhanging side wall surface 41 which is formed by the frusto comcal configuration of the cavity 19. When the cavity 19 is formed by rotation of the tool 31 about the axis of the tool and about an axis spaced from the axis of the tool, it will be apparent that the side wall 41 will be of frusto conical configuration throughout the entire extent thereof.

In the present instance, it is proposed to project the tool 31 into the head 13 in such manner that the thin edge of the cavity 19 will intersect the plane surface 27 on a chord 42 which spans less than of the configuration of the cavity. The side wall 41, therefore, will extend from the opposite ends of the chord 42 throughout more than 180 of the arcuate extent of the side wall-41.

.It is proposed to position the heads 13 on the cylinders 12 in such manner that the chords 42 at the thin edges of the cavities 19 will intersect the ends of the cylinders 12 adjacent one side of the cylinders 12. Then it is proposed to position the cavities so that the outer extremities of the side walls 41 of the cavities will substantially follow the curvature of the outer ends of the cylinders 12. Since the tool 31 is smaller than the diameter of the cavity 19 the cavity will not be widened at the thin end thereof by movement of the tool inwardly and outwardly along the surface 39. Hence the pockets heretofore formed at the thin ends of the cavities and outwardly beyond the peripheral limits of the ends of the cylinders 12 will not be formed.

It is considered preferable to locate the spark plugs 43 in the cavities 19 between the valves 21 and 22 and a considerable distance from the larger ends of the cavities 19 so that the charges that are compressed in the combustion chamber of the engine will commence to burn as near as possible to the center mass of the charge in cavities 19.

The claims:

1. A combustion chamber for internal combustion engines and formed in an engine head, said combustion chamber being of frusto conical formation and extending into said head with the larger end thereof disposed inwardly and the smaller end thereof disposed outwardly of a wall of said head adapted to be secured to the end of an engine cylinder, said combustion chamber comprising an end wall surface and a side wall surface,

formed in said wall of said head, said side wall surface being substantially a frusto conical surface of revolution formed about an axis normal to the plane of said end Wall surface, said surface of revolution being formed to extend throughout more than 180 of the peripheral extent of the frusto conical surface forming said side wall surface.

2. A combustion chamber for internal combustion engines as defined by claim 1 and in which said end Wall surface is substantially a plane surface.

3. A combustion chamber for internal combustion engines as defined by claim 1 and in which said axis of said surface of revolution is disposed obliquely to the axis of said cylinder of said engine and to the surface of said wall adapted to be secured to said cylinder.

4. An internal combustion engine comprising an engine cylinder having a head and a piston adapted .to reciprocate in said cylinder, said head being formed to provide a plane surface on an inner wall thereof and adapted to be secured to the end of said cylinder and normal to the axis of said cylinder, a combustion chamber formed between said head and said piston and said cylinder and including a cavity formed in said wall of said head, said cavity being formed to include an end surface and a side surface with said end surface being disposed obliquely to the axis of said cylinder and intersecting said end of said cylinder upon a chord less than a diameter extending across one side of said cylinder, said side surface being formed to provide a surface of revolution extending throughout the peripheral extent .of said side surface and from one end to the other end of said chord, said surface of revolution being an obliquely disposed conical surface having the base thereof formed by said end surface and the thereof disposed obliquely to said end wall surface of said head and to the axis of said cylinder said cavity being positioned in said head and with respect to the end of said cylinder with the intersection between said conical surface and said plane wall surface of said head substantially following the end of the inner surface of said cylinder.

References Cited in the file of this patent 

